This invention relates to silver halide photographic light-sensitive materials, and more particularly, to silver halide photographic light-sensitive materials having improved shelf life.
In general, silver halides used in silver halide photographic light-sensitive materials are chemically sensitized to provide the desired sensitivity and gradation. A number of chemical sensitization methods are known in the art, including sulfur sensitization using a compound containing sulfur capable of reacting with silver ions and active gelatin, reduction sensitization using a reducing substance, noble metal sensitization using compounds of gold and other noble metals, and combinations thereof. The sulfur sensitizers may include thiosulfates, thioureas, thiazoles, rhodanines, and analogues, and illustrative examples thereof are disclosed in U.S. Pat. Nos. 1,574,944; 2,410,689; 2,278,947; 2,728,668; 3,656,955; 4,030,928; and 4,067,740. The reduction sensitizers may include stannous salts, amine salts, hydrazine derivatives, formamidine sulfinic acid, silane compounds, and analogues, and illustrative examples thereof are disclosed in U.S. Pat. Nos. 2,487,850; 2,419,974; 2,518,698; 2,983,609; 2,983,610; 2,694,637; 3,930,867; and 4,054,458. For noble metal sensitization, there may be used complex salts of gold and complex salts of the metals of Group VIII in the Periodic Table, for example, platinum, iridium, and palladium, and illustrative examples thereof are disclosed in U.S. Pat. Nos. 2,399,083 and 2,448,060 and British Patent No. 618,061.
It was successively proposed to improve these well-known sensitization techniques by the combined use of such compounds as
thiocyanates, PA0 thioethers as disclosed in U.S. Pat. No. 3,021,215, PA0 thion compounds as disclosed in Japanese Patent Publication No. 59-11892 and Japanese Patent Application Kokai No. 53-144319, PA0 imino compounds as disclosed in Japanese Patent Application Kokai Nos. 56-1042 and 57-82833, PA0 benzenesulfinic acid and derivatives, PA0 benzenethiosulfonic acid and derivatives, and PA0 N-halo compounds as disclosed in Japanese Patent Application Kokai No. 51-41056, PA0 cation exchange resins such as Amberite IR-120 (trade name, manufactured by Rohm & Haas); PA0 anion exchange resins such as Diaion SA-21A (trade name, manufactured by Mitsubishi Chemicals K.K.) and Dowex 1.times.8 (trade name, manufactured by Dow Chemicals); PA0 amphoteric resins; and PA0 chelate resins such as Diaion CR-20 (trade name, manufactured by Mitsubishi Chemicals K.K.). PA0 active carbon, active alumina, PA0 activated clay, silica adsorbents (preferably water-resistant), PA0 zeolite adsorbents, porous glass, and porous ceramics.
thereby achieving further sensitization and controlled fogging.
Since all the amount of these chemical sensitizers and chemical sensitization aids added does not react to completion, chemical sensitization continues for an eternity.
The reaction is generally controlled by changing reaction environments, for example, reducing temperature or changing pH and pAg. In order to terminate chemical sensitization at the point of time when the desired photographic property is reached, it has been a common practice to add stabilizers and antifoggants, for example, organic heterocyclic compounds such as azaindenes (e.g., 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene), azoles (e.g., benzimidazoles, benztriazoles, benzthiazoliums, etc.), and mercapto compounds (e.g., mercaptotetrazoles, mercaptotriazoles, mercaptobenzimidazoles, mercaptopurines, etc.); and spectral sensitizing dyes and desensitizing dyes such as cyanine dyes and merocyanine dyes while effecting the reaction control by environmental changes.
Although the further progress of chemical sensitization is prevented by the addition of these compounds, there remain unreacted chemical sensitizers and chemical sensitization aids in a silver halide emulsion. Thus the chemically sensitized silver halide emulsion often changes its photographic properties with the lapse of time when it is stored in a refrigerator until it is coated onto a support, when it is being heated in solution form just before it is coated onto a support (that is, during so-called solution aging), or when it is stored after being coated onto a support.
Even those silver halide emulsions which have not been chemically sensitized often change their photographic properties with the lapse of time under the influence of compounds and concomitant impurities added during the preparation of silver halide grains.
Under these circumstances, there is the increasing need of improving the shelf stability of silver halide emulsions.